1. Technical Field
This invention relates to an apparatus which is moveable to engage opposite sides of a workpiece to perform fabricating operations. More specifically, the apparatus has a tool and anvil which are moveable to engage opposite sides of the workpiece with equal pressure.
2. Prior Art
Various prior art patents have disclosed different apparatus for applying equalized pressure to opposite surfaces of a workpiece during fabrication operations. Such patents include U.S. Pat. Nos. 3,270,640; 3,299,247; 3,396,260; 3,008,032; 3,008,034; 3,136,879; and 4,098,161; each being incorporated herein by reference. In each of the above patents means are provided to equalize the forces applyed to the workpiece to minimize or eliminate distortion of the workpiece when fabricating operations are performed.
Prior tools having equalizing systems are complex apparatus having a linearly displaced tool which is interconnected with an anvil or tool backup member. The interconnection between the tool and anvil have previously included a biasing means, such as a spring, and frame members which are linearly slidable relative to each other. Generally, prior equalizing systems used elongate biasing means which are mounted on the tool parallel to the direction of tool movement. The linearly slidable frame members are used to interconnect the tool to the biasing means. As a result the prior art tools are elongate members that are difficult to maneuver into position to engage a workpiece.
In many situations it is necessary to move such an apparatus into engagement with a workpiece. For instance, on an automobile assembly line the workpiece is typically a partially assembled automobile which is continuously moved along an assembly line. Apparatus used on assembly lines must be maneuverable into position to perform an operation on the automobile and then retracted from the automobile as it moves down the line. Elongate shaped apparatus are cumbersome to maneuver into position for assembly line operations.
The prior art fails to disclose a simply constructed compact apparatus which is effective to align a tool and anvil on opposite sides of a workpiece. U.S. Pat. No. 3,008,034 to Wolfbauer discloses an apparatus for tilting a tool having an equalizing system into position to engage a workpiece. The apparatus disclosed in Wolfbauer in an elongate member having parallel force applying means and equalizing means which are interengaged by linearly moveable frame members. As a result the device is bulky and consequently difficult to maneuver into position. The Wolfbauer apparatus is a welding gun having opposed electrodes mounted on two separate frame members. The frame members of the Wolfbauer welding gun are slidable relative to each other with one of the frame members engaging the gun drive mechanism while the other frame member engages the equalizing system. The frame members are relatively slidable to equalize the pressure exerted by the two opposed electrodes on the workpiece. As such, the Wolfbauer device includes a large number of moveable parts which are subject to wear. As the moveable parts wear, the accuracy of the tool is reduced. The tipping mechanism of the Wolfbauer device includes cam slots that are open to the exterior of the device which allows foreign matter to be deposited on the cam surfaces. Foreign matter on the cam surfaces can lead to accelerated wear of the cam surfaces. In addition, since the cam slots extend completely through the frame members the frame members are weakened making the device subject to distortion from bending stresses developed in the operation of the device.
Accordingly, the prior art has evidenced certain shortcomings and disadvantages when applied to fabrication operations in which the tool must be maneuvered into position to operate on a workpiece.